1. Field of the Invention
The present invention relates to an alloy for bonding wire used to connect a semiconductor chip and a lead frame and, more particularly, to a gold-based alloy for bonding wire of a semiconductor device which is excellent in the strengths at room temperature and under hot conditions after bonding, capable of controlling the ball size to be smaller in bonding, and preventive of a short between wires.
2. Discussion of Related Art
The material generally used for the bonding wire of a semiconductor device is made of an alloy prepared by adding elements (hereinafter, referred to as "dopant") of several PPM or several scores of PPM to the at least 99.999% highly purified gold, and its mechanical properties depend upon the type and amount of the dopant to be added.
To select a wire appropriate to the characteristic of package is of great importance since there are so many kinds of semiconductor packages and each type of wire has its bonding methods.
As the semiconductor chips have been highly miniaturized and the semiconductor mounting techniques with high density have been rapidly developed in recent years, the number of terminals to be connected with bonding wire becomes increased, and accordingly, the gap between the pads gets much smaller in addition to the miniaturization of bonding pad itself. There is thus an increasing demand for bonding wire satisfying the above requirements.
The following characteristics are required in accordance with the trend of semiconductor package as described above.
First, the bonded wire is required to be high in the strengths at room temperature and under hot conditions with the gap between bonded wires getting smaller, so as not to be bent or get curved.
Second, it is needed to control the ball size smaller in bonding, bring the bond strength excellent after bonding, with reduction in the gap between the pad to be bonded. Moreover, the increased bonding length and decreased bonding gap demand us to minimize the sweeping of epoxy-mold wire for the prevention of a short between the wires.